Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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8209-2~
This invention relates to means for distributing steam on a moving
sheet of paper.
In most paper products it is clesirable to automatically control the
cross machine moisture content using a steam sho~Yer or steam clistributor.
Most paper machines have continuous moisture scanners which read the sheet
moisture content across the machine as the paper is manufactured. The
information from this continuous measurement can be fecl into a controlling
computer and the steam flow in the steam distributor can be automatically
controlled according to this inEormation.
Une type oE steam distributor is taugh-t in ll,S, I'atent ~,2~3!2~l7.
The patent teaches a multi-chamberecl steam llood ~Yith means o:E steal.l dis-
tribution to each chamber provicled hy a steam distributor. Steam ~lo~Ys from
the steam distributor through ports into a nozæle and into each chalnber.
The steam -Elo~Y is controlled by raising or lo~Yering a control plug.
A vacuum bo~ is located on the side of the paper opposite the steam
hood so that a vacuum can be applied to pull steam through the paper. The
vacuum is normally applied only IYhen steam is introcluced into -the steam
distributor. I:E, ho~Yever, due to mechanical failure or operator error the
steam ~lo~Y is stopped ~Yhile vacuutn continues to be appliecll sufficient
2n suction coulcl be produced to pull the distributor onto the moving web oE
paper. This could result in damage to the paper ancl to the Fourdrinier ~Yire.
An ob~ect of the present invention is to provide a s-team distribu-tion
system Wit]l vacu~llll release means to prevent the clistriblltor from being pulled
onto the paper IYeb by vacuum.
According to a broad aspect of the present invention there is providecl
a system Eor distributing steam on a paper \Yeb, the system comprising:
a) a hoocl locatecl to one side of the paper wel);
b) means to in-troduce steam into the hoocl;
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c) vacuum box means located to the side of the web opposite said
hood to apply a vacuum to the web;
d) vacuum release means coupled to said hood to:
i) permit a substantial flow of air to enter said hood when
vacuum is applied to said vacuum box means wllile steam is not being introduced
into said hood; and,
ii) restrict the flow of air into said hood wheil steam is being
introduced into said hood.
The invention will now be described in greater detail with reference
to the accompanying drawings, in which:
Figure 1 is a schematic view of a paper making machine including a
steam distributor;
Figure 2 is an isometric illustration of a present embodiment;
Figure 3 is a cross sectional illustration of a present embodiment;
Figure 4 is a detail of part of the embodiment shown in Figure 3; and
Figure 5 is a cross sectional illustration of another embodiment.
There is shown in Figure l a paper making machine 10 including a hot
gas distributor 12. In practice steam is normally used; however in some
applications other hot gases could be substituted. ~lerein the word steam will
be used to mean steam or such other hot gas. The machine sho~n is of the
Fourdrinier type and includes a pulp box 14 feeding pulp mixture 16 to a web-
like conveyor lS on w}lich the li~uid is drawn from the pulp to leave a paper web
20, which travels partially driecl under the distributor 20 and over vacuum box
22, a press section 26, further dryers (not shown) and a known moisture measur-
ing device ~not ShOtYII~ which measures the moisture content acToss the sheet.
The distributor is adjusted manually or automatically to reduce the moisture
variations in the cross direction.
As shown in Figure 2 the steam distributor 12 includes a hood 38
~47~6
having end plates 30 at each end~ each supported ~y a pair of legs 32
carried by feet 34 mounted on the conveyor frame (not shown) outside the
path of the conveyor. A pipe 36 is supported by the end plates 30. A
steam pipe 40 supplies a hot gas, in the present instance, steam from a
suitable source to the pipe 36, As shown in Figure 3, the hood 38 includes
outer shell 42, an inner shell 44 and insulation 46 which together form
side walls 47 and 49. Transverse partitions 48 divide the hood into a
plurality of chambers or compartmerts 50 spanning the entirc width of the
web 20. As shown in Figure 3, tubes 52, inclividual to the compartments
having ports 51 each supplies steam to its compartment in accordance with
the setting of a pneumatic valve 56 individual to that chamber and controlled
by the moisture profile measuring device or manually, The steam travels
through the pipe 36, through ports 51 into the tubular nozzles 52, through
the nozzles into the chambers 50, through slotted, arcuate diffusing plates
60, through the web 20 and a supporting screen or vacuum box cover 62 forming
the top of vacuum box 22. 'I'he diftusion plates 60 may be drilled plates of
different patterns. I'he plates may be omitted to leave an open bottom
chamber.
Details of the valves 56 are not ta~lght herein and can be ascertained
from U.S. Patent 4,253,247, discussed above. Other known types of valves
are also suitable.
Flgure 3 shows vacuum release means formed in the sidewalls 47 and
49. The sidewalls 47 and 49 of the chamber 50 are spaced apart from paper
web 20 so that spaces 70 and 72 are formed therebetween. In practice, I have
found it desirable to space the sidewalls 47 and 4~ about four inches above
the paper web 20. Hinges 74 and 76 are mounted along the bottoms of side
walls 47 and 4g and plates 78 and 80 are a~'fixed one to each hinge.
The plates are oE sufficient height to extend from the hinges to about three
quarters of an inch above the paper web 20.
E:igure ~ shows details of the hinge 76, which is substantially the
same as hinge 7~. The hinge 76 includes a plurality of cylinders g2 welded
to the plate 80 and a plurality of similar cylinders 8~ welded to the side-
wall ~9. The cylinders 82 are spaced apart from one another and the cylinders
8~ are located betl~een them. Also~ the cylinders ~2 and 8~1 are slightly
spaced apar-t from one another. ~ rod 86 is inserted through the cylinclers
82 and 8~ to Eol~m the pivot member.
In operation, steam is introduced into the hood 38 and vacuum is
applied to the vacuum box 22 so that the pressure in the hood is near ambient.
In this case the plates 78 and 80 are vertical as indicated by plate 7S in
Figure 3 so that no substantial quantity of steam escapes to the atmosphere
and no substantial quantities oE ambient air enter the hood~ ~lowever, if
through operator error or mechanical failure s-team is not introduced thro-lgh
pipe 36 while vacuum is applied to the box 6~, ambient air is drawn into the
hood as indicated by the arrows, and the plate is opened by the air ~low as
shown by plate 80. Thus the vacuum does not exert downwarcl force on the hood
38. It should be understood that the down~ard force on the hood 38 could be
extreme, if not for the present invention. ~or example, Eor a hood 60 inches
in width and 300 inches in lengtll 90,000 pounds of ~orce woulcl be exerted by
a vacuulll of ~ive pounds per s~uare inch, wllich is not uncommon.
In some applications it could be necessary to have only one plate
78 or ~0 rather than both plates, In such a case side~rall ~7 or ~9 would
extend downward to near the paper mat 20. However, in practice I have found
it generally desirable to utilize two plates which will move slightly to
accommodate high spots in the paper mat thus insuring tha-t the mat will not
build up agains-t a siclewall.
Figure 5 illustrates another embocliment in which plates 82 and 84
are similar to plates 78 and 80. However, plates 82 and 84 have upper por-
tions 86 and 88 which c~tend above the hinges 74 ancl 76. The upper portiorls
86 and 8c. are constructed to conform to the lower parts of sidewalls 47 and
49 and to prevent the lower parts of the plates from swinging outwardly,
Thus the plates 82 and 84 prevent the escape of substantial c~uantities of
steam even if the steam pressure becomes high in the hood.
